South African men who have sex with men (MSM) are an understudied population in HIV/AIDS epidemiological and social science research. However, evolving evidence indicates that sexual risk behavior among these men is common, and strongly associated with the use of alcohol. Self-report data suggest that HIV prevalence in this population is as high as or higher than the overall high rate of infection among the general South African population. Due to the association of HIV/AIDS with poverty, African MSM in townships seem to be at particular risk for HIV infection. As a result of these gaps in our knowledge, there is a lack of targeted, culturally appropriate, evidence-based interventions addressing HIV risk in this population and the resources for effective prevention are limited. The aims of the proposed study are (1) to assess the prevalence of HIV among African MSM living in South African townships and identify which behavioral, psychosocial, and network characteristics distinguish infected MSM from non-infected MSM; (2) to identify the structural and psychosocial correlates of sexual risk behavior in these men, with a particular focus on the role of alcohol use; and (3) to describe the social organization of same-sex sexual practices of these men and identify structural and psychosocial factors that affect how these practices are experienced; To accomplish these aims, the proposed study combines HIV testing, a survey, and ethnography. Using ethnographic observations, ethnographic mapping, in-depth interviewing and of 20 key informants and 80 members from the target population, we will first study the lives of African MSM in four townships that are part of the Tshwane Municipality (the greater metropolitan area that includes Pretoria). Ethnography will elucidate how male same-sex sexuality and risk is structured in terms of practices, identities, networks, and communities, and inform future development or adaptation of prevention strategies. Building on the ethnographic phase, we will survey 500 men residing in Tshwane who engage in same-sex sexual practices with men (either exclusively of or in conjunction with sexual interactions with women) recruited via Respondent-Driven Sampling. The survey will identify structural and psychosocial correlates, particularly the role of the use of alcohol and other substances in sexual risk behavior. HIV testing of survey participants will allow us to identify risk factors of HIV infection, enabling us to target HIV prevention efforts to specific behaviors, subgroups of MSM, or their female partners, and to determine the correspondence between the study participant's presumed and actual serostatus. In the final phase of the proposed study and based on the study's outcomes, the research team will in collaboration with community partners design an intervention; feasibility and effectiveness of this intervention will be tested in a subsequent study. 1